(a) Field of the Invention
The present invention relates to an omnidirectional antenna.
(b) Description of the Related Art
In general, a spiral antenna that is used for a wireless transmission apparatus exhibits wideband characteristics and has simple parameters for production to be widely used. Such a spiral antenna is produced by forming a metal pattern of a spiral structure at a substrate of a plane structure, and is an antenna in which a main radiation direction is formed in a direction perpendicular to the plane. A Radio Frequency (RF) power supply unit of such a spiral antenna is located at the center of the spiral antenna.
However, because an antenna that is mounted in a terminal or a communication node of a general mobile communication system or sensor network system requires omnidirectional radiation characteristics, the antenna uses an antenna of a monopole or dipole shape, and the plane antenna is changed and used to correspond to a shape of a communication apparatus so as to exhibit omnidirectional radiation characteristics. However, because a size of such an antenna should be about ¼ of a wavelength of a frequency used, the size of the antenna increases.
A plane inverse F-type antenna and an internal PCB antenna have a simple structure and a small size, but have a small frequency bandwidth and a small antenna gain and do not represent an omnidirectional radiation shape by interference or electromagnetic mutual coupling with a cover or an internal component of a wireless transmission apparatus.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.